So it turns out a spinner wrote the first full draft of the government's WMD dossier, after all. And what a pedigree John Williams has: former political editor of the Daily Mirror, friend of Alastair Campbell and one of Whitehall's most energetic and fearsome press officers - and now a contributor to this site.

The Foreign Affairs Committee, the Intelligence and Security Committee, Lord Hutton and Lord Butler all failed to recognise the role he played in writing the dossier. But thanks to Christopher Ames, a charity researcher from Surrey, we now know the truth: Williams wrote a substantial draft of the dossier on the September 9 2002, which has never been disclosed by the Foreign Office. So while Williams played a bit part in Lord Hutton's inquiry into the death of government scientist David Kelly, he should really have had a starring role.

We will not know the full significance of the Williams draft until it is released. There is the outside possibility that it could just contain a series of doodled notes, but it has been suggested that it runs to 50 pages. Does it contain the now discredited claim that Iraq could deploy biological and chemical weapons within 45 minutes?

Williams says not (and will say so again in a response to this). But, in a sense, this is just a detail. The very existence of the document demonstrates that the government was not entirely open with Hutton or the Butler inquiry into the use of intelligence. Williams' draft is a direct challenge to the government's assertion that the intelligence services had full "ownership" of the dossier.

Williams was as close to the Blairite spin machine as it was possible to get. If, as it seems, he wrote the first substantial draft of the document that was used to persuade the British public (and parliament) to go to war, then it changes everything.

There now needs to be full disclosure of Williams' involvement in the dossier: not just the draft of September 9, but right through to its publication just before parliament was recalled on that fateful day in late September. He may provide the key to the whole sorry affair.